To me, DW was just another dragon. Admittedly an awesome looking dragon made out of armor platting and lava, but just a dragon. Threatening to destroy the world had simply been admiting my inevitable victory, I was just there as a witness.

Theramore. Theramore hit me like no raid boss ever has (except the Essence of Anger in BT. That thing haunted my nightmares for weeks). My goblin went first, and capped his victory by watching an Alliance city explode! Then I got on my worgen, and as I queued up, it suddenly occurred to me that I was about to LOSE. Outside of BGs (which are inherently meaningless) that just didn't happen. It's left an impression on me.

No, it doesn't. It's still Horde against Horde. Now, if the rebellion chose to join the Alliance as a political entity, that would be a different matter, but at that point it would also cease to be a rebellion.